1. Field of the Invention
The present invention relates to an apparatus and a method for representative temperature measurements in same-type tubular reactors filled with solid particles, at least one tubular reactor containing a temperature measuring unit.
2. Description of the Related Art
Exothermal reactions such as oxidation reactions on an industrial scale are often, on the grounds of heat transfer and the narrow residence time distribution, carried out in tubular reactors (compare eg. U.S. Pat. No. 3,147,084, German Patent No. 11 85 590 and German Patent No. 29 03 582), the reaction volume usually being located within the tubes and the space between the tubes having a fluid heat transfer medium flowing through it for heating or cooling purposes. In general the reaction is carried out as a gas phase reaction with the aid of a heterogenous catalyst. The catalysts used are generally unsupported catalysts or support materials of identical geometrical shape and coated with active material. Such reactors are employed in the chemical industry, for example, in the production of phthalic anhydride from o-xylene or the production of acrolein or acrylic acid from propene or propane (compare eg. DE-A-1 962 431 and DE-A- 2 943 707).
Any assessment of the state of the reactor, of the product quality to be expected and of the conversion ratio relies strongly on the temperature along the flow path of the reacting component in the reactor. This temperature profile is usually obtained by means of a thermocouple or a resistance thermometer. For industrial use, the thermocouple or resistance thermometer is mechanically protected against damage. To this end it is usually fitted within a thermometer protection sleeve. Such a thermometer sleeve does have the drawback, however, that it occupies a certain volume and consequently, in general, will alter the flow profile and thus the pressure drop behavior of the tube including its charge. Since, on the other hand, it is important that the temperature measurements be carried out on one or more tubular reactors which are representative of all tubular reactors, the reaction process in the tubular reactor in which the temperature is measured is required to be identical with the process in the tubular reactors without a temperature measuring unit.